2-46 BOAT HULL DESIGN 



Side Deck and Deck Edge or Gunwale. 



Vertical Loading - Assume a 200 lb. man at the center of the longest span 

 Factor of Safety = 4. 



200 LBS 



63' 



SECTION A-A 



Fig. 2-24. Gunwale - assumed section for vertical loading 



Bending Moment, M = S& = 20 °, x 63 = 3150 in. -lbs. (2.7) 



Consider the same laminate as the Fore Deck. 



From a detailed calculation the cloth in tension is critical 

 and controls the strength of the section. 



Ultimate tensile strength F tu = 2J,,100 psi. (Table 5-6) 



Consider only the vertical flange to be effective: 



Section Modulus. Z = t h (2.29) 



6 



Recuired, Z = 31 -° x ll = 0.523 in. 3 (2.22) 



2li,100 



To find reauired depth, h, where t is the equivalent thickness 

 if the laminate were all cloth 



h2 = 6Z = 6 x 0.523 = 31 .Jj sq . in . (2.29a) 



t 0.100 



h = 5.60 in.; use 5-5/8 in. deep coaming; Fig. 2-25 



Horizontal Loading: Assume weight of boat concentrated at center of longest span; 

 island to motor well. 



From a detailed calculation the cloth in compression is the critical material. For 

 an explanation of the use of tensile and compressive stresses, rather than flexural 

 stresses, see Design Example 2-1; Gunwale and Thwart Design. 



Factor of Safety = 2.0 



Weight of Boat; estimated = 2000 lbs. 



Bending Moment, M = & = 2 °°° * 63 = 31,500 in. -lbs. (2.7) 



Ultimate Compressive Stress, F cu = 18900 psi from Table 5-11 



Required Section Modulus, Z = 31 ^9° X 2 = 3.33 in. 3 (2.22) 



Actual Section Modulus of section shown in Fig. 2-25; from 

 detailed calculation, Z = U.65 in. 3 Satisfactory 



